In certain applications, a user may need to monitor the status of an activity, function, variable, or other data by relying on auditory, as opposed to visual, indicators. For example, in many situations requiring physiological monitoring, such as in the course of surgery, providing anesthesia, or tracking critical vital signs, a user needs to visually focus on tasks other than monitoring and, therefore, is unable to visually monitor the physiological data for important changes or variations. In such cases, the monitoring of physiological data may best be achieved through the sonification of physiological data. Sonifying data generates auditory indicators by expressing received information as humanly perceptible sound patterns.
An exemplary physiological data monitoring device is a pulse oximeter. Pulse oximeters are used to monitor and report on blood flow characteristics including, but not limited to, the level of arterial blood saturation, the volume of individual blood pulsation supplying a tissue, and the rate of blood pulsation corresponding to each heartbeat. Where important changes or variations occur in blood flow characteristics, it would be valuable to indicate such changes or variations using auditory indicators such that health care providers, including doctors, nurses, technicians, and other persons, can be warned of a patient's health status without having to constantly visually monitor the pulse oximeter.
Oximeters typically comprise monitoring units that incorporate modules for generating audible alarm signals when a particular physiological parameter varies beyond certain safe limits. These oximeters use well-defined audio signaling techniques for the limited purpose of conveying alarm situations. For example, an existing oximeter generates a tonal signal that has a pitch proportional to the ratio of oxygen saturation and a sequential repetition proportional to pulse.
However, a continuous variation of audio pitch with the level of oxygen saturation (SpO2) does not allow a user to effectively associate a particular tone with a certain SpO2 reading. Also, prior art oximeters use special-purpose monitor units that incorporate audio generation circuitry, often implemented in hardware, that offer limited scope for manipulation of various acoustic variables governing an audio signal.
Therefore, an approach to physiological data monitoring is needed whereby audio signals are generated that represent predetermined transition points over a range of physiological data measurements, such as a range of SpO2 measurements. It is further needed to implement a sonification system in software such that the alarm signals can be programmed or manipulated by a user and such that the sonification system can be used on any general-purpose computing device such as a PC, PDA or a laptop computer.